﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Security.Cryptography;

namespace SoTaiChinh.Library.Common.Cryption
{
    public class MD5Cryption
    {
        public MD5Cryption()
        { }
        public string Encrypt(string source)
        {            
            using (MD5 md5Hash = MD5.Create())
            {
                string hash = GetMd5Hash(md5Hash, source);
                //Console.WriteLine("The MD5 hash of " + source + " is: " + hash + ".");
                //Console.WriteLine("Verifying the hash...");
                if (VerifyMd5Hash(md5Hash, source, hash))
                    return hash;
                else
                    return null;
            }
        }
        private string GetMd5Hash(MD5 md5Hash, string input)
        {
            // Convert the input string to a byte array and compute the hash.
            byte[] data = md5Hash.ComputeHash(Encoding.UTF8.GetBytes(input));
            // Create a new Stringbuilder to collect the bytes
            // and create a string.
            StringBuilder sBuilder = new StringBuilder();
            // Loop through each byte of the hashed data 
            // and format each one as a hexadecimal string.
            for (int i = 0; i < data.Length; i++)
            {
                sBuilder.Append(data[i].ToString("x2"));
            }
            // Return the hexadecimal string.
            return sBuilder.ToString();
        }

        // Verify a hash against a string.
        private bool VerifyMd5Hash(MD5 md5Hash, string input, string hash)
        {
            // Hash the input.
            string hashOfInput = GetMd5Hash(md5Hash, input);
            // Create a StringComparer an compare the hashes.
            StringComparer comparer = StringComparer.OrdinalIgnoreCase;
            if (0 == comparer.Compare(hashOfInput, hash))
                return true;
            else
                return false;
        }
    }
}

//How to use
//static void Main(string[] args)
//    {
//        string source = "Hello World!";
//        using (MD5 md5Hash = MD5.Create())
//            {
//                string hash = GetMd5Hash(md5Hash, source);
//                Console.WriteLine("The MD5 hash of " + source + " is: " + hash + ".");
//                Console.WriteLine("Verifying the hash...");
//                if (VerifyMd5Hash(md5Hash, source, hash))
//                    Console.WriteLine("The hashes are the same.");
//                else
//                    Console.WriteLine("The hashes are not same.");
//            }
//    }